The present invention relates to a method for obtaining a composite material comprising a first continuous strip of a film of a polymeric material and a second continuous strip exhibiting low adherence towards adhesives and substantially of the same length as said first continuous strip and having a thickness that is at least several times greater than the thickness of said film, a continuous layer of adhesive being provided between said first and second strips, the second continuous strip being sufficiently wide to at least cover said adhesive, the adhesive having a power of adhesion to said 15 second continuous strip that is distinctly less than its power of adhesion to the material constituting said first continuous strip. It also relates to a roll of composite material obtained by carrying out the above method and to an adhesive tape obtained from said roll.
Such adhesive tape is particularly suitable for use in splicing of two films, the ends of which are close but are not in abutment, of a very thin material such as a polymeric material film subjected to biaxial stretching, marketed under the trade name Mylar.RTM., notably when the film that has been spliced in this way is required to go through winding or 5 unwinding apparatus at very high speed, while optionally being simultaneously slit longitudinally into narrower widths. Any notable excess thickness in the region of the joint upsets smooth running of the film or requires the speed at which it is traveling to be considerably reduced which is obviously not desirable. Such incidents occur when conventional adhesive tapes having a thickness of around 30 .mu.m are employed.
It is currently necessary to join a polymeric material films of extremely small thickness (around 2 .mu.m, the thickness of certain Mylar.RTM. films sometimes being as low as 0.9 .mu.m), using an ultra-thin tape. However, the provision of such an adhesive tape of extremely small thickness gives rise to considerable technical problems. Indeed, when dealing with such small thicknesses, the support that is to receive the adhesive, in other words the tape's substrate or body is practically impalpable and has practically no self-sustaining or mechanical properties because it is so thin (less than 3 .mu.m). Under such conditions, deposition of an adhesive by conventional means, for example by surface application, is impossible.
One object of the present invention is to provide a method for obtaining an ultra-thin adhesive tape that allows a substrate of extremely reduced thickness to be used, such thickness being less than 5 .mu.m and preferably of the order of 2 .mu.m.
A further object of the invention is to enable an ultra-thin polymeric film substrate to be employed for this purpose said film being marketed under the trade name Mylar.RTM..
A further object is to provide an adhesive tape that is particularly suitable for splicing the non-abutting ends of very thin films of plastics material, for example webs or films in Mylar.RTM. material, the adhesive tape being able to be readily handled prior and during this operation.
Another object of the invention is to provide a method for obtaining an adhesive tape and a roll of composite material used for dispensing lengths of adhesive tape that make it possible to splice two very strong and extremely thin plastics material films, such as Mylar.RTM., which are arranged in close proximity to each other without touching and are positioned extremely accurately, whereby splicing of two films of equal width placed notably in perfect axial alignment can be achieved.